Flushing pigments



Patented Jan. 27, 1942 FLUSHING PIGMENTS Edward G. Yee, Chicago, IlL, assignor to The Sherwin-Williams Company, Cleveland, Ohio,

a corporation of Ohio No Drawinx.

Application October 5, 1939, Serial No. 298,056

Claims. (Cl. 106-5262) The present invention relates to improvements in the manufacture of non-aqueous pigment dispersions in a liquefiable vehicle, and particularly to the transfer of aqueous pigment pulps directly into organic vehicles by an operation or process known to those skilled in the art as flushing." It has special reference to agents for effecting and/or facilitating the transfer.

It is well known that some pigments may be I flushed into oil without an added flushing agent. For example, aqueous white lead is readily flushed into linseed oil by simply mixing the two materials. Pigments in this class are usually hydrophobic in character. It is also known that certain agents facilitate the flushing operation, or even bring it about in the case of certain combinations of pigments and receiving vehicle. Pigments which do not flush easily or require agents to effect the transfer, are hydrophilic in character. Various explanations are given for the success of such agents or class of agents and for the failure of chemically similar compounds. Some of these explanations involve the physical nature of the molecule as well as its chemical' reactivity.

The present invention is based upon the discovery that a group of amines not heretofore known as flushing agents are useful as such. The value of the invention lies in the facts that a relatively small quantity is needed to effect the transfer, and that the flushing agent is relatively inexpensive.

The object of the invention is to use as flushing agents amines or their soaps having the essential grouping where R1 and R2 may be hydrogen, methyl, or benzyl groups, or combinations thereof.

It is also an object of the invention to form pigment dispersions characterized by the pres-- volves intimate mixing of the aqueous pigment pulp and the receiving vehicle at a considerable expenditure of time and power. Aflushing agent quickens the process and saves time and money. There is a frequent tendency of the vehicle and water to emulsify in such operations. Hastening the process minimizes emulsiflcation. The formation of emulsion decreases the efficiency of the flushing operation, because more water is retained in the mass, which water must be removed by other means. One use of the flushing agent is to minimize or prevent the formation of emulsion.

Pigments particularly suitable for flushing in accordance with this invention are iror blues, chrome yellows, organic lakes and pigmentdyestuffs.

The vehicle may be any water-immiscible liquid or solid which is or becomes liquid at the temperature of operation. It may be selected from coal tar solvents, mineral spirits, hydrogenated naphthas, representing the volatile vehicles, or from linseed oil, China wood oil, soya bean oil, perilla oil, other vegetable and animal oils, synthetic and oleoresinous varnishes, representing the drying vehicles, or mineral oil, petrolatum, castor oil and waxes, representing the non-drying vehicles. All these may be used in the present invention. The drying oils ordinarily have an acid number, representing a content of fatty acid which may form a soap with the amine flushing agent. The formation of the soap does not render the amine ineffective, for the amine agent may be added effectively as a soap or as the free amine. The amine may be condensed with soap-forming fatty acids such as oleic, stearic, palmitic, linoleni'c, ricinoleic acid, or with soap-forming resin acids, such as rosin or abietic acid, to form the amine soap flushing agent.

Because the free amine or its soaps may be used with vehicles which are volatile or which possess no acid number, it is known that both the free amine and its soaps are flushing agents. While soap formation is not essential for the practice of this invention, some acidity in neutral vehicles adds to the effectiveness of the amine flushing agents, where the acid is of a soapforming character. Thus, fatty acids or other soap-forming acids may be added.

Examples are given below to illustrate this invention. While these examples deal mainly with iron blue pigments, its usefulness is not restricted to such. Iron blue (ferric ferrocyanide) is highly hydrophilic and is one of the most.

diflicult pigments to employ in a flushing process. Therefore, the invention is illustrated largely by reference to it, as itis the severest test found to measure the comparative effectiveness of the flushing agents.

mixing continued. In a short time, usually less than twenty minutes, the water in the presscake will separate or "flush out and the iron blue is taken up by the varnish. The water is de= canted off or removed by other means, and about one third ofthe remaining presscake is addedv to the mixerf At this stage, 50 lbs. of litho varnish and 2 lbs. of benzylamine are also added. On further mixing, more water is flushed out. The remaining presscake is flushed out in two charges in the above manner, using 2 lbs. of benzylamine and -50 lbs. of litho varnish in each charge. When all the presscake is flushed, steam is turned on and the temperature of the mass raised to 50-60 C. Vacuum is applied to the mixer and mixing is continued under reduced pressure until the pigment-oil paste is substantially water-free. The mass is cooled and the remaining 100 lbs. of litho varnish added to make a base ink containing one part of pigment to one part of varnish. This is a typical procedure for the practice of this invention, but it is not restricted to such. Those skilled in the art will vary this procedure to suit their own need. In-

stead of vacuum drying, the paste may be finished upon a roller mill., The time-cycle for this procedure is about four hours.

EXAMPLE II 2000 lbs. of water-wet iron blue presscake cont given result varies with the apparatus used, the

taming 500 lbs. of the pigment (dry basis), 500

lbs. litho varnish, 25 lbs. dibenzylamine.

The procedure is similar to that of Example I.

EXAMPLE III 2000 lbs. of water-wet iron blue presscake containing 500 lbs. of the pigment (drybasis), 500 lbs. mineral oil, 15 lbs. benzyl N-dimethyl amine, 25 lbs. oleic acid. The oleic acid and the benzyl dimethyl amine are mixed to form a benzyldimethyl oleate soap with an excess of the free amine. From this point on, the procedure is similar to that of Example I. The amine soap and mineral oil are added to the mixer as needed.

- EXAMPLE IV 3000 lbs. of water-wet medium chrome yellow containing 2000 lbs. of the pigment (dry basis), 500 lbs. linseed oil, 10 lbs. benzylamine.

The procedure is similar to that of Example I.

EXAMPLE V amine may be primary, secondary or tertiary,-so

long as it has at least one benzyl radical. This establishes that the eifectlve grouping is curtain-N in a free amine or in an amine soap. The agents may have solubility in water, but are generally more soluble in the liquid vehicle. The -removal of water from the mass after a flushing operation may'remove some of the agent. However, where the operation is conducted in one step. its main function has been performed. Where the operation is carried out in several steps more of the agent is added, so that any removal of some of the agent in the withdrawn water cannot be effective to deplete the process of the agent.

The oil pastes prepared in the manner described are suitable for the manufacture of all types of protective'and decorative finishes, and for allied applications.

The quantity of flushing agent required for a pigment, the pulp concentration, the receiving vehicle, and other factors. It is a small quantity, commonly less than 5% of the dry weight of pigment.

The practice may be varied in accordance with the scope of the invention as expressed in the appended claims.

I claim:

1. The method of flushing pigment particles from aqueous paste form into aliquid vehicle immiscible with water to release water, which comprises agitating a mass of aqueous pigment paste with a receiving liquid vehicle which is immiscible with water, in the presence of a small quantity of a benzylamine compound having the grouping therein with the formula R1 CeH CHr-N in which R1 and R2 may be selected from the group consisting of hydrogen, and the radicals: methyl and benzyl.

2. The method of flushing pigmentparticles from aqueous paste form into a liquid vehicle immiscible with water to release water, which comprises agitating a mass of aqueous pigment paste with a receiving liquid vehicle which is immiscible with water, in the presence of a small quantity of a benzylamine compound of the formula.

in which R1 and R: may be selected from the group consisting of hydrogen, and the radicals: methyl and benzyl.

3. The method of flushing pigment. particles from aqueous paste form into a liquid vehicle immiscible with water to release water, which comprises agitating a mass of aqueous pigment paste with a receiving liquid vehicle which is immiscible with water, in the presence of a small quantity of a benzylamine soap of a benzylamine of the formula in which R1 and Rz-may be selected from the group consisting of hydrogen, and the radicals:

methyl and benzyl, and a soap-forming acid se- 7. The method according to claim 1 in which lected from the group of soap-forming resin one of the attachments R1 and R: is hydrogen. acids and soap-forming fatty acids. 8. The method according to claim 1 in which 4. The method according to claim 1 in which the compound is benzylamine. the receiving liquid contains a drying vehicle for 5 9. The method according to claim 1 in which pigment. the receiving liquid is litho varnish.

5. The method according to claim 1 in which 10. The method according to claim 1 in which the receiving liquid is a non-drying vehicle for the pigment is iron blue. pigment.

6. The method according to claim 1 in which 10 EDWARD G. YEE.

5 the receiving vehicle is volatile. 

